Get type of a variable in Kotlin

kotlin instanceof
matteo picture matteo · Jul 18, 2017 · Viewed 34k times · Source

How can I find the variable type in Kotlin? In Java there is instanceof, but Kotlin does not exist:

val properties = System.getProperties() // Which type?

Answer

Willi Mentzel picture Willi Mentzel · Jul 18, 2017

You can use the is operator to check whether an object is of a specific type:

val number = 5
if(number is Int) {
   println("number is of type Int")
}

You can also get the type as String using reflection:

println("${number::class.simpleName}")    // "Int"
println("${number::class.qualifiedName}") // "kotlin.Int"

Please note:

On the Java platform, the runtime component required for using the reflection features is distributed as a separate JAR file (kotlin-reflect.jar). This is done to reduce the required size of the runtime library for applications that do not use reflection features. If you do use reflection, please make sure that the .jar file is added to the classpath of your project.

Source: https://kotlinlang.org/docs/reference/reflection.html#bound-class-references-since-11

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